Safety device for elevator cars



May 5, 1970 R. GABLER SAFETY DEVICE FOR ELEVATOR CARS 3 Sheets-Sheet 1 Filed Feb. 23 1968 INVENTOR Rudolf Gabler B Rum R. GABLER SAFETY DEVICE FOR ELEVATOR CARS May 5, 1970 Filed Feb. 23 1968 3 Sheets-Sheet z INVENTOR Rudolf 60MB! B): Mum M M May 5, 1970 R. GABLER SAFETY DEVICE FOR ELEVATOR CARS 3 Sheets-Sheet 5 Filed Feb. 23 1968 INVENTDR M2, 601220 5 WWW United States Patent 3,509,970 SAFETY DEVICE FOR ELEVATOR 'CARS Rudolf Gabler, Heiden, Switzerland, assignor to Aufzuege AG Schaifhausen, Schatfhausen, Switzerland Filed Feb. 23, 1968, Ser. No. 707,619 Claims priority, application Switzerland, Mar. 16, 1967, 3,7 98/ 67 Int. Cl. B66b /16 US. Cl. 187--90 13 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The invention relates to an elevator safety-device for mounting on each side of the car and cooperating with a respective guide rail,'and having a pair of rotatable clamping jaws which can be released in dependence on the car speed to clamp under resilient pressure on the guide rail.

Among the elevator safety-devices of the prior art, there are devices that .incorporate wedge-shaped clamping jaws, which, when contacting the guide rail, rotate on bearings to a spring-loaded end position. The angle of the wedge must not exceed a certain value. The wedges, therefore, must have an appreciable length and must be well guided. In addition, the bearings must be protected from dirt and the introduction of foreign particles, which necessitates a more complicated construction.

The :prior art also numbers among the elevator safetydevices, a device in which the clamping jaws are built as eccentrics, which take a tangential position in their end position. As against the wedge-shaped clamping jaws, it is impossible with this design to control the actual clamping force, as result of which the gripping surfaces of the eccentric badly scores the guide rail as they slide therealong.

SUMMARY OF THE INVENTION -An object of. the invention is an elevator-car safetydevice which avoids the above-mentioned disadvantages.

In the invention, each clamping jaw is constructed as a brake pressure plate that rotates about an axis transverse to the guide rail when the plate is pressed against the rail, the plates being located side by side with the rail located therebetween, andv apart of eachv of the inner faces of the plates being pressed against the rail when the safety device is actuated.

In a preferred embodiment of the invention each brake pressure plate incorporates a helically-shaped bearing surface located on the outer face of the plate, and a pressure roller bearing on each bearing surface, and rotating thereon when the plate rotates, in the region opposite where the plate is pressed against the rail.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described in detail, with reference to the figures of the accompanying drawing, wherein:

FIG. 1 is a view of the safety device, unactuated as seen from the guide-rail side;

FIG. 2 is a side view of the safety device;

FIG. 3 is a view corresponding to FIG. 1 of the safety device actuated;

FIG. 4 is a view in section taken along line IVIV of FIG. 3; l

3,509,970 Patented May 5, 1970 DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the FIGS. 1 to 5, the elevator car (not shown) is guided by a pair of rails 1, of which only one is illustrated. The car is equipped with two similar safety devices, one on each side of the car and acting on a respective rail. Only one safety device is shown. Two brake pressure plates 2:: and 2b, located on respective sides of the guide rail 1 which projects part way between them, are rotatably mounted on a bolt 9 that serves as the mounting axle for the pressure plates. The plates are so mounted that they are free to shift axially along the length of the bolt 9, being kept apart by a relatively weak helical spring 17 in compression, so that the plates, when the safety device is not in operation, do not bear upon the respective guide rails 1. The outer face of each pressure plate 1 incorporates a helicallyshaped bearing surface or cam track 4, which butts against a rotatably mounted pressure roller 5 arranged as a cam follower on one end of an arm 6. The other end of the respective arm is pivotally connected to the housing 3 of the safety device. The bolt 9 extends transversely through the two arms 6 by means of openings therein, as shown in FIG. 5. A helica'l spring 8 mounted on the bolt urges the two arms 6 together. Two cup springs 7, also mounted on the bolt, are first put under appreciable stress when the arms 6 are forced apart by the pressure plates 2a and 2b as the safety device is applied. Each arm 6 incorporates a stop 12 (FIGS. 1 and 3), which bears on the stop cam -14 of an actuating lever 13, when the safety device is out of operation. The lever 13 is connected at one end to a shaft 15 joined to a connecting rod 16 that leads to an identical actuating lever of the other safety device. With the'safety device unactuated, the arms 6, under spring tension, bear against the stop cam 14, and the pressure plates are forced by the compression spring 17 against the pressure rollers 5.

The tension applied by the springs 7 and 8 against the arms 6 can be varied by adjusting, in any suitable and known manner, the position of the collar (not referenced), on which the spring 8 is mounted, along the length of the bolt 9.

The inner face, which acts on the guide rail 1, of each brake pressure plate 2a and 2b incorporates over the larger part of its circumference a sharply serrated surface 10. The actual brake shoes 11 are wider than the surface 10, as shown in FIG. 4, and their exposed faces have sharp-edged grooves 11a. The shoes advantageously are made as replaceable parts. A spiral torsion spring 18 is arranged coaxially with respect to the compression spring 17 in each pressure plate 2a and 2b. The torsion springs maintain the pressure plates in the position shown in FIGS. 1 and 2, before the safety device is applied, wherein the start of each bearing surface 4 is urged against the respective pressure roller 5 and the start of the surfaces 10 lie opposite the guide rail 1.

The safety device operates in the following manner. The actuating lever 13 is connected in the customary way via a rope to a speed governor. If the car speed exceeds a permissible value, the rope pivots the lever 13 upwards.

3 The stop cam 14 thus frees the stops 12, and the levers 6 are urged together by the spring 8. The pressure rollers press the brake pressure plates 2a and 2b against the guide rail 1 in opposition to the bias of the weaker spring 17. The surfaces of the plates 2a and 2b press against the rail 1; and the plates 2a and 2b begin to turn, whereby the pressure rollers 5 turning on the cam track or bearing surface 4 are forced outwards, causing the springs 7 and 8 to be more and more compressed. When the plates 2a and 2b have been turned to their end positions, in which the brake shoes 11 grip the guide rail 1 and the stops 19 prevent further rotation of the pressure plates, the stress of the springs 7 and 8 is at its maximum adjustable value at which the car is braked until it is stopped.

As the car is raised, after having been brought to an emergency stop by the safety device, the brake pressure plates are turnedback to their starting positions until the stops 12 of the levers 6 bear on the stop cam 14. The pressure plates 2a and 2b are released and, after freeing their grip on the guide rail, are speed completely apart by the spring 17 and rotated back to their starting positions by-spring 18. A lever 22 connected to the shaft is biased by a helical spring 23, which returns the actuating lever 13 to its initial position. A second lever 20 can be mounted on the lever 13 for operating a switch 21 for shutting off the power to the elevator motor, when the lever 13 is pivoted upwards.

FIG. 6 shows a second embodiment of the safety device of the invention. This form differs from the preceding only in the construction of the actuating means. Instead of an-actuating lever 13 having a stop cam 14 borne upon by two stops 12, there is provided on the bolt 9 a sleeve 26 located between the two arms 6. The sleeve incorporates an outwardly projecting cam 27 on each end. When the safety device is not applied, the earns 27 bear on the inner face of the respective arm 6. The arms incorporate each a recess which a respective cam 27 can enter when the sleeve 26 is sufiiciently rotated. The sleeve rotation is caused by a rope connected to the speed governor. To this end, a release shaft 29, arranged in a bore in the bolt 9, is connected at its exposed end to a lever 30 to which the rope is secured. A cam 28, projecting into a groove 26a of the sleeve 26, is mounted on on the other end of the shaft 29. A second lever 31 mounted on the shaft 29 transmits 'via a rod 32 the actuating movement to the other safety device. In this embodiment, the two brake pressure plates 2a and 2b are urged by a common spring 33 against the rollers 5 and also rotated back to their starting positions after an emergency stop by the safety device. A switch 34, operated directly by the plate 2a, can be provided for cutting off the current.

Tests have shown that the operation of these two forms of the invention is greatly dependent on the amount of friction between the brake pressure plates and the guide rail. The value varies greatly not only between greased and ungreased rails but also during the course of the operating life of the elevator. Particularly noteworthy are the difference in the coefficient friction between parts of the guide rail that are caked with grease and other parts that are rusted or rough. In these conditions it is scarcely possible to adjust the safety device correctly.

The embodiment of FIGS. 7 to 9 automatically adjusts to a wide range of coeflicients of friction, by reducing the force with which the brake pressure plates grip the guide rails when the coefficient is high, and thereby limiting the maximum braking force.

The construction of this embodiment is quite similar to the two preceding forms. A pair of arms 6, mounting pressure rollers 5 on their ends, is arranged on the bolt 9. Two brake pressure plates 2a and 2b, each having more or less the shape of a segment, are mounted on the bolt. In FIG. 8 the position of the plate 2b is shown in dotdash line When the safety device is not actuated, and in full line when actuated. As again the two embodiments of FIGS. 1 to 6, the bolt 9 mounts only one cup spring 7, which presses the arms 6 towards, and therefore the pressure rollers 5 against, the brake pressure plates 2a and 2b, so that the latter clamp on the guide rail 1 when the actuating means (not shown) is operated.

When the safety device is applied the nose-shaped ends 2 of the plates 2a and 2b bear against a plunger 35 loaded by a spring 36. The arms 6 incorporate a V-shaped groove 6b behind the pressure rollers 5. A wedge-like member in the form ofa cylinder 37 embodying a slanting face 38 at each end is located in a bore of the pressure plates 2a and 2b and in a groove 9b of the bolt 9. In addition, a cylinder 39 which bears on the face 38 of the cylinder 37 is located in each groove 6b.

This embodiment of the invention operates in the following manner. When the pressure plates are located in braking position, with their ends 2] bearing on the plunger 35, the latter shifts as soon as the braking force exerted on the plunger by the plates 2a and 2b exceeds the force of the spring 36 on the plunger. As a result, the plates 2a and 2b pivot somewhat, whereby the slanting faces 38 of the cylinder 37, via the cylinders 39, slightly spreads apart the two arms 6 against the force of the spring 7, thereby reducing the force of the rollers 5 on the plates 2a and 2b and decreasing the braking force. Should the coeflicient of friction between the guide rail 1 and the plates 2a and 2b decline, so will the braking force. The spring 36 then forces the plunger 35 back to its normal position, and the brake pressure plates pivot back to their normal position in operation. As a result, the cylinder 37 no longer plays its role, and the spring 7 again plays its full role, as a consequence of which the rollers 5 press more firmly on the pressure plates and the braking force rises. The safety device of the invention enables setting the maximum braking force to any desired value by adjusting the tension of the spring 36 by means of screws 40'.

What is claimed is:

1. In an elevator including a car traveling along an upright guide rail, a safety device on said car engageable with said rail for braking the car, and actuating means for engaging the safety device with said rail when the downward speed of car movement exceeds a predetermined speed, the improvement in the safety device which comprises:

(a) two plate members having respective inner faces directed toward each other and respective outer faces directed away from each other;

(b) mounting means mounting each plate member on said car for rotation about an axis transverse of said faces of the plate member and transverse of the direction of said ear movement, and for axial movement toward and away from the other plate member, a portion of the inner face on each plate member spaced from the associated axis being axially aligned with said rail,

(1) whereby frictional engagement of said portion with said rail causes rotation of said plate member about said axis;

(c) a substantially helical cam track on the outer face of each plate member about the axis of rotation of the same; and

(d) cam follower means engaging each cam track for axially pressing each plate member against said rail in response to said rotation of the plate member.

2. In an elevator as defined in claim 1, each cam follower means including an arm having two ends, one of said ends being movably mounted on said car, a pressure roller rotatably mounted on the other end, and resilient means holding said roller in engagement with said cam track.

3. In an elevator as defined in claim 2, said mounting means including a bolt member rotatably supporting said plate members, said arms being formed with respective bores intermediate said ends thereof, said bolt member passing through said bores.

4. In an elevator as defined in claim 2, said portion of said inner face being sharply serrated in an arc about said axis and carrying a brake shoe.

5. In an elevator as defined in claim 4, said brake shoe having an exposed face formed with sharpedged grooves.

6. In an elevator as defined in claim 2, a lever member mounted for being pivoted by said actuating means between an inactive and an active position, cooperating abutment means on said arms and on said lever for holding said arms apart and for thereby disengaging said plate member from said rail in the inactive position of said lever member, and spring means pressing said arms and the pressure rollers thereon against said cam tracks and thereby engaging said inner faces with said rail when said lever member is in the active position thereof.

7. In an elevator as defined in claim 2, torsion spring means biasing said plate members toward respective angular positions in which the associated pressure roller engages the portion of said cam track nearest said inner face.

8. In an elevator as set forth in claim 2, said mounting means including a bolt member having an axis and rotatably supporting said plate members, said arms being formed with respective bores intermediate said ends thereof, said bolt member passing through said bores, a sleeve coaxially rotatable on said bolt member and connected to said actuating means for rotation thereby between two angular positions, two cams on said s eeve abuttingly engaging said arms in one of said angular positions for holding the arms apart and for thereby holding said plate members out of engagement with said rail, said cams releasing said arms in the other angular position of said sleeve, and spring means pressing said released arms and the pressure rollers thereon against said cam tracks and thereby frictionally engaging the inner faces of said plate members with said rail.

9. In an elevator as set forth in claim 8, said sleeve being located between said arms, and said cams projecting from respective axially terminal portions of said sleeve.

10. In an elevator as defined in claim 7, connecting means for connecting said sleeve to said actuating means, said bolt member being hollow, and said connecting means including a release shaft rotatably mounted in said bolt, and motion transmitting means for transmitting rotary motion from said shaft to said sleeve.

11. In an elevator as defined in claim 1, cooperating abutment means on each plate member and on said car for stopping the rotation of said plate members caused by said frictional engagement in a first angular position, resilient means backing the abutment means on said car and dimensioned to yield when the frictional forces engaging said plate members with said rail exceed a predetermined value, whereby said plate members move further from said first angular position toward a second angular position and friction decreasing means responsive to said further movement of the plate members for urg ing the plate members away from said rail, and for thereby decreasing said frictional forces.

12. In an elevator as defined in claim 11, each cam follower means including an arm having two ends, one end being movably mounted on said car, a pressure roller rotatably mounted on the other end, spring means pressing said arms and the pressure rollers thereon against said cam tracks and thereby biasing said inner faces toward frictional engagement with said rail, and securing means securing said arms against rotation about the axes of said plate members, said friction decreasing means including wedge means secured to said plate members for rotation therewith and engaging said arms for urging the same away from each other against the restraint of said spring means in response to movement of said plate members from said first toward said second angular positions thereof.

13. In an elevator as defined in claim 12, said mounting means including a bolt member rotatably supporting said plate members, said arms being formed with respective bores, portions of said bolt member being received in said bores and constituting said securing means.

References Cited UNITED STATES PATENTS HARVEY C. HORNSBY, Primary Examiner 

